The principal objectives of this proposal are to gain a clearer and broader understanding of the coupling of blood flow and metabolism, with particular emphasis on the role of adenosine in this complex process, the factors involved in the formation, release and mechanism of action of adenosine and the effect of adenosine on parenchymal tissues. Specifically we will 1) determine the tissue interstitial fluid concentrations of adenosine and its influence on coronary blood flow in various experimental conditions, 2) utilize "micro" adenosine deaminase to evaluate the role of adenosine in blood flow regulation, 3) determine the sites of production (extracellular vs. intracellular) and cell compartmentation of adenosine with use of isolated perfused hearts, dispersed myocytes, and fat cell ghosts, 4) characterize the external and internal adenosine receptors with the use of nonmetabolizable adenosine analogues and polymers of adenosine, 5) examine the regenerative Ca++ gating as affected by phosphoinositides in atria, islets of langerhans and chromaffin cells and the role played by adenosine in the regulation of phospholipid turnover, 6) study the affect of adenosine on chloride transport in the dogfish rectal gland and in the lung to determine whether the water movement associated with chloride transport can be of importance in pulmonary edema, 7) measure regional cortical adenosine production and cerebral blood flow in visual and somatosensory cortex during graded photic and sciatic nerve stimulation, respectively, and the effect of theophylline on factors influencing cerebral blood flow, 8) determine the relative contribution of cerebral endothelial and glial cells in the production of adenosine with respect to their function in the regulation of cerebral blood flow, 9) assess the contribution of presynaptic and postsynaptic activation on the release of adenosine from sympathetic ganglia and to examine the effects of adenosine on presynaptic and neuronal Ca++ currents, 10) examine the effect of cross innervation of red and white muscle on 5 feet-nucleotidase activity and how this might alter vascular responses in muscle function as well as determine the influence of endothelial or arterioles in organ culture on induction of 5 feet-nucleotidase activity in skeletal muscle.